Complete wavefront reconstruction using sequential intensity measurements of a volume speckle field

Percival Almoro, Giancarlo Pedrini, and Wolfgang Osten

Percival Almoro,1 Giancarlo Pedrini,1 and Wolfgang Osten1

1All the authors are with the Institut für Technische Optik, Universität Stuttgart, Pfaffenwaldring 9, Stuttgart 70569, Germany. P. Almoro (almoro@ito.uni-stuttgart.de) is on leave from the National Institute of Physics, University of the Philippines,
Diliman, Quezon City 1101, Philippines.

Abstract

The recording of the volume speckle field from an object at different planes combined with the wave propagation equation allows the reconstruction of the wavefront phase and amplitude without requiring a reference wave. The main advantage of this single-beam multiple-intensity reconstruction (SBMIR) technique is the simple experimental setup because no reference wave is required as in the case of holography. The phase retrieval technique is applied to the investigation of diffusely transmitting and reflecting objects. The effects of different parameters on the quality of reconstructions are investigated by simulation and experiment. Significant enhancements of the reconstructions are observed when the number of intensity measurements is 15 or more and the sequential measurement distance is
0.5
mm or larger.
Performing two iterations during the reconstruction process using the calculated phase also leads to better reconstruction. The results from computer simulations confirm the experiments. Analysis of transverse and longitudinal intensity distributions of a volume speckle field for the SBMIR technique is presented. Enhancing the resolution method by shifting the camera a distance of a half-pixel in the lateral direction improves the sampling of speckle patterns and leads to better quality reconstructions. This allows the possibility of recording wave fields from larger test objects.

Nonreconstructions obtained from two intensity measurements separated by 0.5 and 1.0 mm, despite the large number of iterations. For comparison, the images at right show good reconstructions when multiple intensity measurements are used.